.... onto state property to detect,....
You got me curious, so I went to the FMDAC's state-by-state list, to look up WI. Because quite often, some of the states on this list will say something like "With permission" or "with a permit". But when you look deeper into it (their supporting footnotes that lead to their actual rules/laws), you find NO SUCH THING.
So in other words, it's just commentary, not actual rule. And you know how this list from the FMDAC evolved don't you ?? It's traced back to the VERY ORIGINS (of "swatting hornet's nests") that I speak of. That eventually led to wonderful lists like this.
Here's the WI page :
http://www.fmdac.org/wisconsin-state-regulations.html
It started in the early (or mid ?) 1980s. When a fellow named Doc R. Grim wrote a book called "Treasure laws of the United States". He attempted to create an alphabetic listing, of all 50 states, detailing their state's park's laws/rules, regarding the use of detectors in their state parks. So that that way: RV travelers, that go state to state, can have an immediate reference.
Great idea, eh ? Who can argue with that, eh ? Save you the embarrassment of breaking a law. Or conversely give you peace of mind to know that it was allowed in other states parks you were passing through. And you could show any busy-body, who attempted to hassle you, the "yes" straight from their state capitol head honcho. Brilliant Idea, right ?
And guess the method that the author used to get his information (back in the era before the internet) ? Drum-roll: Easy, he asked. Yup, he merely xeroxed off 50 letters, and sent them to the head office P.R. person, in each state capitol's head-of-parks. The letter was to the effect of : "I am writing a book detailing the laws/rules, regarding the use of metal detectors in all the 50 state's state parks. Can you please tell me what, if any rules, govern the use of detectors in your state parks."
And then he just sat back and waited for 50 replies to fill his post box. Brilliant idea right ? Can't argue with an answer "straight from the dept. themselves", right ?
But when the book came out, you had a lot of old-timers scratching their heads saying "since when ?". And some of the answers coming back incoherent like "with permission at each kiosk" (yet when you went to check on the source/citation, that was nowhere to be found). And perhaps they'd point you to something about "disturbing wildlife" or "lost and found" laws, blah blah. At places that, quite frankly, had never been an issue before.
And the current FMDAC list is merely a continuation of that starting genesis kernal. And sure, perhaps by now (35+ yrs. later), it's now being codified and 'made official' in some states like yours. Moral of the story ? LET'S ALL STOP SWATTING HORNET'S NESTS.